Device and method for reducing vibration in a compressor

ABSTRACT

A device and method for reducing vibration in a compressor are provided. The device for reducing vibration in a compressor may include a compressor controlled to be operated at a target operating velocity after starting; a power supply that supplies power to the compressor; and a controller that controls the power supply so that a magnitude or a phase of the power supplied to the compressor is changed. The controller may control the power supply so that vibration generated in the compressor is offset by an exciting force generated in the compressor within a predetermined time interval multiple times when the compressor starts or when the compressor stops during a target operation velocity operating of the compressor.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority under 35 U.S.C. 119 and 35U.S.C. 365 to Korean Patent Application No. 10-2013-0010013, filed inKorea on Jan. 29, 2013, which is hereby incorporated by reference in itsentirety.

BACKGROUND

1. Field

A device and method for reducing vibration in a compressor are disclosedherein.

2. Background

A refrigeration cycle is a series of cycles of compression,condensation, expansion, and evaporation, and is used in an airconditioner. The air conditioner may perform heating using condensationheat of refrigerant and perform cooling using evaporation heat.

A device that compresses the refrigerant in the refrigeration cycle is acompressor. The compressor is connected with a condenser or anevaporator by a pipe through which the refrigerant flows in therefrigeration cycle.

As the compressor, a constant-velocity compressor and an invertercompressor are primarily used, and a velocity control pattern for theconstant-velocity compressor and inverter compressor is illustrated inFIG. 1 according to the related art. FIG. 1A is a graph illustrating anoperating velocity of the compressor with time when operating theconstant-velocity compressor, and FIG. 1B is a graph illustrating anoperating velocity of the compressor with time when operating theinverter compressor.

Referring to FIG. 1A, the constant-velocity compressor is abruptlyaccelerated up to the operating velocity in starting and abruptlystopped in stopping. Referring to FIG. 1B, the inverter compressor isaccelerated up to the operating velocity relatively slowly as comparedwith the constant-velocity compressor, but abruptly stopped in stoppinglike the constant-velocity compressor.

FIG. 2A illustrates a velocity control pattern for a constant-velocitycompressor according to the related art. FIG. 2B illustrates an excitingforce generated in a compressor by the velocity control pattern of FIG.2A. FIG. 2C illustrates vibration generated in a compressor by thevelocity control pattern of FIG. 2A. FIG. 2D illustrates stress thatacts on a pipe connected with a compressor due to the velocity controlpattern of FIG. 2A.

Referring to FIGS. 2A-2D, the exciting force acts on the compressor whenthe compressor starts and stops, and as a result, the compressorvibrates and stress having the same pattern as the vibration of thecompressor acts on the pipe connected with the compressor. Therefore,when the compressor is operated according to the velocity controlpattern according to the related art, the stress acts on the pipeconnected with the compressor whenever the compressor starts or stops,and as a result, the pipe may be broken.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the followingdrawings in which like reference numerals refer to like elements, andwherein:

FIGS. 1A-1B are graphs illustrating an operating velocity pattern of acompressor according to the related art, FIG. 1A illustrating theoperating velocity pattern in the case of a constant-velocitycompressor, and FIG. 1B illustrating the operating velocity pattern inthe case of an inverter compressor;

FIG. 2A illustrates a velocity control pattern for a constant-speedcompressor according to the the related art;

FIG. 2B illustrates an exciting force generated in a compressor by thevelocity control pattern of FIG. 2A;

FIG. 2C illustrates vibration generated in a compressor by the velocitycontrol pattern of FIG. 2A;

FIG. 2D illustrates stress that acts on a pipe connected with acompressor due to the velocity control pattern of FIG. 2A;

FIG. 3 is a schematic diagram of a device for reducing vibration in acompressor according to an embodiment;

FIG. 4A illustrates a velocity control pattern for a device for reducingvibration in a compressor according to an embodiment;

FIG. 4B illustrates an exciting force generated in the compressor by thevelocity control pattern of FIG. 4A;

FIG. 4C illustrates vibration generated in a compressor by the velocitycontrol pattern of FIG. 4A;

FIG. 4D illustrates stress that acts on a pipe connected with acompressor due to the velocity control pattern of FIG. 4A.

FIG. 5A illustrates a velocity control pattern by the device forreducing vibration in a compressor according to an embodiment;

FIG. 5B is a graph illustrating a magnitude of current provided to thecompressor for the velocity control pattern of FIG. 5A;

FIG. 6 is a flowchart illustrating a method for reducing vibration in acompressor according to an embodiment;

FIG. 7A is a graph illustrating an acceleration pattern when acompressor velocity is accelerated in two stages;

FIG. 7B is a graph illustrating an acceleration pattern when acompressor velocity is accelerated in three stages;

FIG. 7C is a graph illustrating an acceleration pattern when acompressor velocity is accelerated in four stages;

FIG. 8A illustrates an acceleration pattern of a method for reducingvibration in a compressor according to another embodiment; and

FIG. 8B is a graph illustrating a result of Equation 2 discussed hereinbelow.

DETAILED DESCRIPTION

Hereinafter, a device and method for reducing vibration in a compressoraccording an embodiments will be described in detail with reference tothe accompanying drawings. Where possible, like refernce numerals havebeen used to indicate like elements, and repetitive disclosure has beenomitted.

FIG. 3 is a schematic diagram of a device for reducing vibration in acompressor according to an embodiment. Further, FIG. 4A illustrates avelocity control pattern for a device for reducing vibration in acompressor according to an embodiment.

Referring to FIG. 3, the device for reducing vibration in a compressoraccording to this embodiment may include a compressor 100, a powersupply 200, and a controller 300. The compressor 100 may be connectedwith a pipe 10. For example, the compressor 100 may form a refrigerationcycle together with a condenser 20, an evaporator 30, and an expansiondevice 40 and serve to compress and discharge refrigerant. For example,the compressor 100 may be connected with the condenser 20 and theevaporator 30 through the pipe 10.

The compressor 100 may be operated at a target operating velocity Vpuntil a stop signal is input after starting.

The power supply 200 may serve to supply power to the compressor 100.The power supply 200 may supply power by changing a magnitude and aphase of power provided to the compressor 100 according to a control bythe controller 300 as described hereinbelow.

The controller 300 may control the power supply 200 to damp vibration,which may be generated in the compressor 100, by an exciting force whenthe exciting force is generated temporally separately multiple times,that is, with a difference of a set time at a time when the compressor100 starts or stops. That is, the controller 300 may control the powersupply 200 so that vibration generated in the compressor in starting orstopping is minimized.

Herein, the exciting force generated multiple times may include a firstexciting force (see A in FIGS. 4A-4D) generated in starting, that is,when a starting signal is input into the compressor 100, and a secondexciting force (see B in FIGS. 4A-4D) generated just after the firstexciting force A. The first exciting force A and the second excitingforce B may be generated with a temporal separation which isapproximately ½ of a natural frequency of the vibration of thecompressor 100, for example, as illustrated in FIGS. 4A-4D, that is,approximately half of a period of the natural frequency of thevibration.

The first exciting force A may be an exciting force generated by acurrent applied to the compressor 100, so that the compressor 100 isoperated at a velocity (first velocity, V1), which is half of the targetoperating velocity Vp, as discussed hereinbelow. In addition, the secondexciting force B may be an exciting force generated by a current appliedto the compressor 100, so that the compressor 100 currently operated atthe velocity (first velocity, V1), which is half of the target operatingvelocity, is operated at the target operating velocity Vp. A magnitudeof the first exciting force A may be relatively larger than a magnitudeof the second exciting force B.

As a result, a first vibration C generated in the compressor 100 by thefirst exciting force A may include a first wave a, a second wave b, anda third wave c, as illustrated in FIGS. 4A-4D. In addition, a secondvibration D generated in the compressor 100 by the second exciting forceB may include a first wave a′ and a second wave b′, as illustrated inFIGS. 4A-4D. The second wave b of the first vibration C may be equal tothe first wave a′ of the second vibration D in magnitude and opposite indirection, and as a result, both exciting forces may be offset.Similarly, the third wave c of the first vibration C may be equal to thesecond wave b′ of the second vibration in magnitude and opposite indirection, and as a result, both exciting forces may be offset.

However, the first wave a of the first vibration C generated in a firstinterval I, which is an interval before the second exciting force B isgenerated after the first exciting force A is generated, may not beoffset but may remain. Therefore, stress equivalent to the vibrationgenerated in the compressor 100 may be generated in the pipe 10connected with the compressor 100 in the first interval I. However, allvibration of the compressor 100 may be offset, and thus, not generatedafter the first interval I, and as a result, the stress does not act onthe pipe 10. Therefore, the total stress S that acts on the pipe 10 whenthe compressor 100 starts becomes the stress generated in the firstinterval I, as illustrated in FIGS. 4A-4D.

After the first interval I, the compressor 100 may be operated at thetarget operating velocity Vp until a stopping signal of the compressoris recognized.

Further, the aforementioned generation of the exciting force multipletimes may include a third exciting force (see A′ in FIGS. 4A-4D)generated in stopping, that is, when the stopping signal is input intothe compressor 100, and a fourth exciting force (see B′ in FIGS. 4A-4D)generated just after the third exciting force A′. The third excitingforce A′ and the fourth exciting force B′ may be generated with atemporal separation, which may be approximately ½ of the naturalfrequency of the vibration of the compressor 100, for example, asillustrated in FIGS. 4A-4D, that is, approximately half of a period ofthe natural frequency of the vibration.

The third exciting force A′ may be an exciting force generated by acurrent applied to the compressor 100, so that the compressor 100 isoperated at the velocity (first velocity, V1), which is half of thetarget operating velocity of the compressor 100. In addition, the fourthexciting force B′ may be an exciting force generated by a currentapplied to the compressor 100, so that the compressor 100 completelystops at the velocity (first velocity, V1), which is half of the targetoperating velocity of the compressor 100. A magnitude of the thirdexciting force A′ may be relatively larger than a magnitude of thefourth exciting force B′.

As a result, a third vibration C′ may be generated in the compressor 100by the third exciting force A′, and a fourth vibration D′ may begenerated in the compressor 100 by the fourth exciting force B′. As theaforementioned description of the first vibration C and the secondvibration D may be applied to the third vibration C′ and the fourthvibration D′, repetitive description thereof has been omitted.

Similarly to the first interval I, as a second interval II, which is aninterval before the fourth vibration D′, is generated, the thirdvibration C′ may not be offset but may remain. Therefore, stressequivalent to the vibration generated in the compressor 100 may begenerated in the pipe 10 connected with the compressor 100 in the secondinterval II. However, all vibrations of the compressor 100 may beoffset, and thus, not generated after the second interval II, and as aresult, the stress may not act on the pipe 10. Therefore, a total stressS that acts on the pipe 10 when the compressor 100 stops becomes thestress generated in the second interval II, as illustrated in FIGS.4A-4D.

Therefore, the stress that acts on the compressor 100 and the pipe 10connected to the compressor 100 may be minimized by the device forreducing vibration in the compressor according to embodiments. Further,the first exciting force A and the third exciting force A′, and thesecond exciting force B and the fourth exciting force B′ described abovemay be provided by supplying a current pattern as illustrated in FIG. 5to the compressor 100.

For example, the first exciting force A and the third exciting force A′,and the second exciting force B and the fourth exciting force B′ may begenerated by an impulse current as illustrated in FIGS. 5A-5B; however,embodiments are not limited thereto. Further, the controller 300 mayprimarily accelerate the compressor up to the first velocity V1, whichmay be less than the target operating velocity Vp, at the time ofstarting the compressor 100, and thereafter, secondarily accelerate thecompressor up to the target operating velocity Vp after time haselapsed. A time when the secondary acceleration starts may be a timeafter approximately ½ of the natural frequency of the vibration of thecompressor 100 has elapsed from the time when the primary accelerationstarts. In addition, the first velocity V1 may be approximately half ofthe target operating velocity Vp, and in this case, the vibrationgenerated in the compressor may be minimized as described above.

Further, the controller 300 may primarily decelerate the compressor 100down to the first velocity (see V1 in FIGS. 4A-4D), which is less thanthe operating velocity (see Vp in FIGS. 4A-4D, as the compressor 100 isoperated at the target operating velocity, the operating velocity andthe target operating velocity are equal to each other) when thecompressor 100 stops, and thereafter, secondarily decelerates thecompressor 100 so that the compressor 100 completely stops after thetime has elapsed. A time when the secondary deceleration starts may be atime after approximately ½ of the natural frequency of the vibration ofthe compressor 100 has elapsed from the time when the primarydeceleration starts. In addition, the first velocity V1 may beapproximately half of the operating velocity Vp, and in this case, thevibration generated in the compressor 100 may be minimized as describedabove.

Hereinafter, a method for reducing vibration in a compressor accordingan embodiment will be described in detail with reference to theaccompanying drawings.

FIG. 6 is a flowchart illustrating a method for reducing vibration in acompressor according to an embodiment. Hereinafter, the method forreducing vibration in a compressor according to embodiments is describedon the presumption that an initial state of the compressor 100 is a stopstate, but this is for ease of description and embodiments are notlimited thereto.

Referring to FIG. 6, first, a compressor, such as compresssor 100 ofFIG. 3, which is in the stop state, may be primarily accelerated up to afirst velocity (S100). The first velocity may be a velocitycorresponding to approximately half of a target operating velocity to bedescribed below; however, embodiments are not limited thereto.

In addition, after a time as long as approximately ½ of a naturalfrequency of the vibration of the compressor from a time when theprimary acceleration starts, the compressor may be secondarilyaccelerated up to the target operating velocity. The primaryacceleration and the second acceleration may be achieved by supplying animpulse current corresponding to a maximum current to the compressor,for example. Thereafter, the compressor may be operated while constantlymaintaining the target operating velocity (S300).

Thereafter, the compressor may be primarily decelerated down to a secondvelocity (S400). The second velocity may be a velocity corresponding toapproximately half of a target operating velocity similarly as the firstvelocity; however, embodiments are not limited thereto.

In addition, after a time as long as approximately ½ of a naturalfrequency of the vibration of the compressor from a time when theprimary deceleration starts, the compressor may be secondarilydecelerated so that the compressor completely stops (S500). The primarydeceleration and the secondary deceleration may be achieved by supplyingan impulse current corresponding to a minimum current.

A series of steps from the start to the stoppage of the compressor maybe completed through steps S100 to S500.

Hereinafter, a method for reducing vibration in a compressor accordinganother embodiment will be described in detail with reference to theaccompanying drawings.

FIGS. 7A-7C illustrate an acceleration pattern to be used in a methodfor controlling vibration in a compressor according to anotherembodiment. That is, FIG. 7A is a graph illustrating an accelerationpattern when a compressor velocity is accelerated in two stages, FIG. 7Bis a graph illustrating an acceleration pattern when a compressorvelocity is accelerated in three stages. FIG. 7C is a graph illustratingan acceleration pattern when a compressor velocity is accelerated infour stages. Further, FIG. 8 is a graph illustrating a result ofEquation 2 discussed hereinbelow.

Hereinafter, accelerating the velocity of the compressor will bedescribed as an example for easy description, but the following contentsmay be applied to even decelerating the compressor.

In a case where the velocity of the compressor 100 is accelerated, whenthe velocity is accelerated as an impulse pattern in two stages, asillustrated in FIG. 7A, the velocity is accelerated as an impulsepattern in three stages, as illustrated in FIG. 7B, or the velocity isaccelerated as an impulse pattern in four stages, as illustrated in FIG.7C, the same effect as the previous embodiment may be achieved. That is,vibration of the compressor may be minimized when the compressor starts.

However, it is extremely difficult to accelerate the velocity of thecompressor using the impulse patterns as illustrated in FIGS. 7A, 7B,and 7C. Therefore, hereinafter, an acceleration pattern g(t) of theimpulse patterns illustrated in FIGS. 7A, 7B, and 7C, and a generalacceleration pattern f(t) are subjected to convolution integral topropose the acceleration pattern for the velocity of the compressor.

In general, the convolution integral as a kind of integral form may beused to acquire an output signal of a linear system for an input signaland an impulse response of the system.

First, the convolution integral is illustrated in Equation 1 below.

[Equation 1]

f(t)* g(t)=∫_(∞) ^(∞) f(t)g(t−τ)dτ

It has been already demonstrated that a new function acquired throughthe convolution integral expressed by Equation 1 above has features ofthe existing f(t) and g(t). When force is excited in two stages asillustrated in FIG. 7A, f(t)=a and g(t)=1/(1+k) (at t=0), andg(t)=k/(1+k) (at t=ΔT). When both functions are subjected to theconvolution integral, a result thereof is illustrated as Equation 2below.

$\begin{matrix}{{{{f(t)}^{*}{g(t)}} = {{\frac{a}{1 + k}{H(t)}} - {\frac{a}{1 + k}{H\left( {t - {\Delta \; T}} \right)}} + {\frac{ak}{1 + k}{H\left( {t - T} \right)}} - {\frac{ak}{1 + k}{H\left( {t - T - {\Delta \; T}} \right)}}}}\mspace{20mu} {{k = ^{\frac{{- \zeta}\; \pi}{\sqrt{1 - \zeta^{2}}}}},\mspace{20mu} {{\Delta \; T} = \frac{\pi}{\omega \sqrt{1 - \zeta^{2}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where ω=natural frequency of compressor vibration system,

ζ=damping ratio of compressor vibration system,

a=maximum acceleration of compressor,

T=V/a, V=target operating velocity,

H(x)=unit step function,

H(x)=1 (x≧0), and

H(x)=0 (x<0).

In FIGS. 8A and 8B, Equation 2 above is expressed by graphs. In FIG. 8A,an equation corresponding to area (A) is a/(1+k)*H(t)−a/(1+k)*H(t−Δt)and an equation corresponding to area (B) isak/(1+k)*H(t−T)−ak/(1+k)H(t−T−ΔT). It can be seen that FIG. 8B isacquired by simply summing up areas (A) and (B).

That is, as illustrated in FIG. 8B, when i) the compressor isaccelerated at a/(1+k) from 0 sec to ΔT sec, ii) the compressor isaccelerated at a from AT sec to T sec, iii) the compressor isaccelerated at ak/(1+k) from T sec to ΔT+T sec, the vibration isgenerated in the compressor similarly as the case in which the velocityis accelerated as the impulse pattern in two stages as illustrated inFIG. 7A. Therefore, the vibration in the compressor may be reduced whenthe compressor is accelerated as illustrated in FIG. 8B.

When force is excited in three stages as illustrated in FIG. 7B, f(t)=aand g(t)=1/(1+2k+k²) (at t=0), g(t)=2k/(1+2k+k²) (at t=ΔT), andg(t)=k²/(1+2k+k²) (at t=2ΔT). When both functions are subjected toconvolution integral, a result thereof is illustrated as Equation 3below.

$\begin{matrix}{{{f(t)}^{*}{g(t)}} = {{\frac{a}{1 + {2\; k} + k^{2}}{H(t)}} - {\frac{a}{1 + {2\; k} + k^{2}}{H\left( {t - {\Delta \; T}} \right)}} + {\frac{2\; {ak}}{1 + {2\; k} + k^{2}}{H\left( {t - T} \right)}} - {\frac{2\; {ak}}{1 + {2\; k} + k^{2}}{H\left( {t - T - {\Delta \; T}} \right)}} + {\frac{{ak}^{2}}{1 + {2\; k} + k^{2}}{H\left( {t - {2\; T}} \right)}} - {\frac{{ak}^{2}}{1 + {2\; k} + k^{2}}{H\left( {t - {2\; T} - {\Delta \; T}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

where ω=natural frequency of compressor vibration system,

ζ=damping ratio of compressor vibration system,

a=maximum acceleration of compressor,

T=V/a, V=target operating velocity,

H(x)=unit step function,

H(x)=1 (x≧0), and

H(x)=0 (x<0).

That is, even when the velocity of the compressor is accelerated asillustrated in Equation 3, the vibration generated in the compressor maybe reduced.

Further, when force is excited in fourth stages as illustrated in FIG.7C, f(t)=a and g(t)=1/D (at t=0), g(t)=3k/D (at t=ΔT), g(t)=3k²/D (att=2ΔT), and g(t)=k³/D(at t=3ΔT). When both functions are subjected tothe convolution integral, a result thereof is illustrated as Equation 4below.

$\begin{matrix}{{{f(t)}^{*}{g(t)}} = {{\frac{a}{D}{H(t)}} - {\frac{a}{D}{H\left( {t - {\Delta \; T}} \right)}} + {\frac{3\; {ak}}{D}{H\left( {t - T} \right)}} - {\frac{3\; {ak}}{D}{H\left( {t - T - {\Delta \; T}} \right)}} + {\frac{3\; {ak}^{2}}{D}{H\left( {t - {2\; T}} \right)}} - {\frac{3\; {ak}^{2}}{D}{H\left( {t - {2\; T} - {\Delta \; T}} \right)}} + {\frac{k^{3}}{D}{H\left( {t - {3\; t}} \right)}} - {\frac{k^{3}}{D}{H\left( {t - {3\; T} - {\Delta \; T}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

where D=(1+k)³.

ω=natural frequency of compressor vibration system,

ζ=damping ratio of compressor vibration system,

a=maximum acceleration of compressor,

T=V/a, V=target operating velocity,

H(x)=unit step function,

H(x)=1 (x≧a0), and

H(x)=0 (x<0).

That is, even when the velocity of the compressor is accelerated asillustrated in Equation 4, vibration generated in the compressor may bereduced.

Embodiments disclosed herein provide a device for reducing vibration ina compressor and a method for reducing vibration that minimize vibrationin a compressor when the compressor starts and stops.

Embodiments disclosed herein provide a device for reducing vibration ina compressor that may include a compressor controlled to be operated ata target operating velocity after starting; a power supply unit or powersupply that supplies power to the compressor; and a control unit orcontroller that controls the power supply unit so that a magnitude or aphase of the power supplied to the compressor is changed. The controlunit may control the power supply unit so that vibration generated inthe compressor is offset because or by an exciting force generated inthe compressor within a predetermined time interval multiple times whenthe compressor starts or when the compressor stops during a targetoperation velocity operating of the compressor.

Further, the predetermined time interval may correspond to approximately½ of a natural frequency of the compressor vibration. In addition, whenthe compressor starts, the multiple times of exciting force may includea first exciting force, and a second exciting force generated after thefirst exciting force is generated and having a smaller magnitude thanthe first exciting force. Moreover, the first exciting force may be anexciting force generated by a current applied to the compressor so thatthe compressor is operated at a first velocity lower than a targetoperating velocity, and the second exciting force may be an excitingforce generated by a current applied to the compressor so that thecompressor operated at the first velocity is operated at the targetoperating velocity. In addition, the first velocity may correspond toapproximately ½ of the target operating velocity of the compressor.

Moreover, when the compressor stops, the multiple times of excitingforce may include a third exciting force, and a fourth exciting forcegenerated after the third exciting force is generated and having asmaller magnitude than the third exciting force. Further, the thirdexciting force may be an exciting force generated by a current appliedto the compressor so that the compressor is operated at the firstvelocity lower than the target operating velocity, and the fourthexciting force may be an exciting force generated by a current appliedto the compressor so that the compressor operated at the first velocitystops. In addition, the first velocity may correspond to approximately ½of the target operating velocity of the compressor.

Further, the multiple times of exciting force may be generated by animpulse current supplied to the compressor.

A device for reducing vibration in a compressor according to anotherembodiment may include a compressor constituting a refrigeration cycleand operable at a target operating velocity; a power supply unit orpower supply that supplies power to the compressor; and a control unitor controller that controls the power supply unit so that a magnitude ora phase of the power supplied to the compressor is changed. The controlunit may control the power supply unit so that the compressor isaccelerated or decelerated to a first velocity which is less than thetarget operating velocity when the compressor starts or when thecompressor stops while being operated at the target operating velocity.

Further, the control unit may control the power supply unit so that thecompressor is primarily accelerated up to the first velocity, andthereafter, secondarily accelerated up to the target operating velocityafter a predetermined time elapsed when the compressor starts. Further,the predetermined time may correspond to approximately ½ of a naturalfrequency of the compressor vibration.

In addition, the control unit may control the power supply unit so thatthe compressor is primarily decelerated down to the first velocity fromthe target operating velocity, and thereafter, stops after apredetermined time elapsed when the compressor stops. Further, thepredetermined time may correspond to approximately ½ of a naturalfrequency of the compressor vibration. Moreover, the first velocity maybe a velocity which is half of the target operating velocity.

A method for reducing vibration in a compressor according to yet anotherembodiment may include primarily accelerating a stopped compressor up toa first velocity; and secondarily accelerating the compressor up to atarget operating velocity. A time as long as approximately ½ of anatural frequency of the compressor vibration from a primaryacceleration start time of the compressor up to a secondary accelerationstart time of the compressor. Moreover, the first velocity may be avelocity which is approximately half of the target operating velocity.

In addition, the method may further include primarily decelerating thecompressor operated at the target operating velocity down to the firstvelocity; and secondarily decelerating the compressor to be completelystopped. Further, a time as long as approximately 1/2 of a naturalfrequency of the compressor vibration may elapse from a primarydeceleration start time of the compressor up to a secondary decelerationstart time of the compressor.

Moreover, a first exciting force of the compressor generated in theprimary acceleration may be larger than a second exciting force of thecompressor generated in the secondary acceleration, and a third excitingforce of the compressor generated in the primary deceleration may belarger than a fourth exciting force of the compressor generated in thesecondary deceleration.

According to embodiments disclosed herein, vibration generated in acompressor may be minimized when the compressor starts and stops.Therefore, stress generated in a pipe connected with the compressor maybe minimized, and as a result, breakage of the pipe may be prevented.

Although embodiments have been described above, embodiments are notlimited to the aforementioned specific embodiments. That is, variouschanges and modifications can be made without departing from the spiritand the scope of the appended claims by those skilled in the art, and itshould be understood that equivalents of all appropriate changes andmodifications belong to the scope.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A device for reducing vibration in a compressor,comprising: a compressor controlled to be operated at a target operatingvelocity after starting; a power supply that supplies power to thecompressor; and a controller that controls the power supply so that amagnitude or a phase of the power supplied to the compressor is changed,wherein the controller controls the power supply so that vibrationgenerated in the compressor is offset by an exciting force generated inthe compressor within a predetermined time interval multiple times whenthe compressor starts or when the compressor stops.
 2. The device ofclaim 1, wherein the predetermined time interval corresponds toapproximately half of a period of a natural frequency of the vibration.3. The device of claim 1, wherein when the compressor starts, thegeneration of the exciting force multiple times includes a firstexciting force, and a second exciting force generated after the firstexciting force and having a smaller magnitude than the first excitingforce.
 4. The device of claim 3, wherein the first exciting force is anexciting force generated by a current applied to the compressor so thatthe compressor is operated at a first velocity, which is lower than thetarget operating velocity, and the second exciting force is an excitingforce generated by a current applied to the compressor so that thecompressor currently being operated at the first velocity is operated atthe target operating velocity.
 5. The device of claim 4, wherein thefirst velocity corresponds to approximately half of the target operatingvelocity of the compressor.
 6. The device of claim 1, wherein when thecompressor stops, the generation of the exciting force multiple timesincludes a third exciting force, and a fourth exciting force generatedafter the third exciting force and having a smaller magnitude than thethird exciting force.
 7. The device of claim 6, wherein the thirdexciting force is an exciting force generated by a current applied tothe compressor so that the compressor is operated at a first velocity,which is lower than the target operating velocity, and the fourthexciting force is an exciting force generated by a current applied tothe compressor so that the compressor currently being operated at thefirst velocity stops.
 8. The device of claim 7, wherein the firstvelocity corresponds to approximately half of the target operatingvelocity of the compressor.
 9. The device of claim 1, wherein thegeneration of the exciting force multiple times is accomplished by animpulse current supplied to the compressor.
 10. A device for reducingvibration in a compressor, comprising: a compressor of a refrigerationcycle and operable at a target operating velocity; a power supply thatsupplies power to the compressor; and a controller that controls thepower supply so that a magnitude or a phase of the power supplied to thecompressor is changed, wherein the controller controls the power supplyso that the compressor is accelerated or decelerated to a firstvelocity, which is less than the target operating velocity, when thecompressor starts or when the compressor stops.
 11. The device of claim10, wherein the controller controls the power supply so that thecompressor is primarily accelerated to the first velocity, and after apredetermined time has elapsed, secondarily accelerated to the targetoperating velocity when the compressor starts.
 12. The device of claim11, wherein the predetermined time corresponds to approximately half ofa period of a natural frequency of the vibration.
 13. The device ofclaim 10, wherein the controller controls the power supply so that thecompressor is primarily decelerated to the first velocity from thetarget operating velocity, and after a predetermined time has elapsed,stops when the compressor stops.
 14. The device of claim 13, wherein thepredetermined time corresponds to approximately half of a period of anatural frequency of the vibration.
 15. The device of claim 10, whereinthe first velocity is a velocity which is half of the target operatingvelocity.
 16. A method for reducing vibration in a compressor,comprising: primarily accelerating a stopped compressor to a firstvelocity; and secondarily accelerating the compressor to a targetoperating velocity, wherein a time as long as approximately half of aperiod of a natural frequency of compressor vibration has elapsed from aprimary acceleration start time of the compressor to a secondaryacceleration start time of the compressor.
 17. The method of claim 16,wherein the first velocity is a velocity which is approximately half ofthe target operating velocity.
 18. The method of claim 16, furthercomprising: primarily decelerating the compressor currently operated atthe target operating velocity to the first velocity; and secondarilydecelerating the compressor to be completely stopped.
 19. The method ofclaim 18, wherein a time as long as approximately half of a naturalfrequency of the compressor vibration elapses from a primarydeceleration start time of the compressor to a secondary decelerationstart time of the compressor.
 20. The method of claim 18, wherein afirst exciting force of the compressor generated in the primaryacceleration is larger than a second exciting force of the compressorgenerated in the secondary acceleration, and a third exciting force ofthe compressor generated in the primary deceleration is larger than afourth exciting force of the compressor generated in the secondarydeceleration.